Having owned both motherboards, I can say from my own experience that AsRock Z77 is a much better board.
I owned the Sabertooth for roughly 3 weeks when it died on me. I would occasionally start my machine and a high pitch loud tone would emit and hold until I turned my machine off. ASUS support just told me is was a hardware fault and that I needed to take it back to the store.
No RMA no additional troubleshooting. My store only has a 14 day return policy on MBs. Had to print off the email correspondence with ASUS to get them to take the board back.
Never touching another ASUS board again. This is my 3rd AsRock board and it will not be my last.
There are 11 people in this world: Those who understand this statement, those who get laid, and the lucky bastards that do both.
Support your local stores, yeah NewEgg is awesome but people put value in dealing with someone face to face and same day delivery.